The Boston public school district has had difficulty maintaining on-time bus service for its students ("A Year Later, School Buses Still Late," Boston Globe, October 5). Suppose the district develops a new bus schedule to help combat chronic lateness on a particularly woeful route. Historically, the bus service on the route has been, on average, 11 minutes late. After the schedule adjustment, the first 25 runs were an average of five minutes late. As a result, the Boston public school district claimed that the schedule adjustment was an improvementstudents were not as late. Assume a population standard deviation for bus arrival time of 11 minutes. The value of the test statistic is __________.

a. z = 2.73 b. t35 = 2.73 c. z = 0.33 d. t35 = 0.33